/* The MIT License

   Copyright (c) 2018 by Attractive Chaos <attractor@live.co.uk>

   Permission is hereby granted, free of charge, to any person obtaining
   a copy of this software and associated documentation files (the
   "Software"), to deal in the Software without restriction, including
   without limitation the rights to use, copy, modify, merge, publish,
   distribute, sublicense, and/or sell copies of the Software, and to
   permit persons to whom the Software is furnished to do so, subject to
   the following conditions:

   The above copyright notice and this permission notice shall be
   included in all copies or substantial portions of the Software.

   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
   EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
   MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
   NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
   BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
   ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
   CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
   SOFTWARE.
*/
#ifndef KETOPT_H
#define KETOPT_H

#include <string.h> /* for strchr() and strncmp() */

#define ko_no_argument       0
#define ko_required_argument 1
#define ko_optional_argument 2

typedef struct {
    int ind;   /* equivalent to optind */
    int opt;   /* equivalent to optopt */
    char *arg; /* equivalent to optarg */
    int longidx; /* index of a long option; or -1 if short */
    /* private variables not intended for external uses */
    int i, pos, n_args;
} ketopt_t;

typedef struct {
    char *name;
    int has_arg;
    int val;
} ko_longopt_t;

static ketopt_t KETOPT_INIT = {1, 0, 0, -1, 1, 0, 0};

static void
ketopt_permute(char *argv[], int j, int n) /* move argv[j] over n elements to the left */
{
    int k;
    char *p = argv[j];
    for (k = 0; k < n; ++k)
        argv[j - k] = argv[j - k - 1];
    argv[j - k] = p;
}

/**
 * Parse command-line options and arguments
 *
 * This fuction has a similar interface to GNU's getopt_long(). Each call
 * parses one option and returns the option name.  s->arg points to the option
 * argument if present. The function returns -1 when all command-line arguments
 * are parsed. In this case, s->ind is the index of the first non-option
 * argument.
 *
 * @param s         status; shall be initialized to KETOPT_INIT on the first call
 * @param argc      length of argv[]
 * @param argv      list of command-line arguments; argv[0] is ignored
 * @param permute   non-zero to move options ahead of non-option arguments
 * @param ostr      option string
 * @param longopts  long options
 *
 * @return ASCII for a short option; ko_longopt_t::val for a long option; -1 if
 *         argv[] is fully processed; '?' for an unknown option or an ambiguous
 *         long option; ':' if an option argument is missing
 */
static int ketopt(ketopt_t *s, int argc, char *argv[], int permute, const char *ostr,
                  const ko_longopt_t *longopts) {
    int opt = -1, i0, j;
    if (permute) {
        while (s->i < argc && (argv[s->i][0] != '-' || argv[s->i][1] == '\0'))
            ++s->i, ++s->n_args;
    }
    s->arg = 0, s->longidx = -1, i0 = s->i;
    if (s->i >= argc || argv[s->i][0] != '-' || argv[s->i][1] == '\0') {
        s->ind = s->i - s->n_args;
        return -1;
    }
    if (argv[s->i][0] == '-' && argv[s->i][1] == '-') { /* "--" or a long option */
        if (argv[s->i][2] == '\0') { /* a bare "--" */
            ketopt_permute(argv, s->i, s->n_args);
            ++s->i, s->ind = s->i - s->n_args;
            return -1;
        }
        s->opt = 0, opt = '?', s->pos = -1;
        if (longopts) { /* parse long options */
            int k, n_exact = 0, n_partial = 0;
            const ko_longopt_t *o = 0, *o_exact = 0, *o_partial = 0;
            for (j = 2; argv[s->i][j] != '\0' &&
                        argv[s->i][j] != '='; ++j) {} /* find the end of the option name */
            for (k = 0; longopts[k].name != 0; ++k)
                if (strncmp(&argv[s->i][2], longopts[k].name, j - 2) == 0) {
                    if (longopts[k].name[j - 2] == 0) ++n_exact, o_exact = &longopts[k];
                    else ++n_partial, o_partial = &longopts[k];
                }
            if (n_exact > 1 || (n_exact == 0 && n_partial > 1)) return '?';
            o = n_exact == 1 ? o_exact : n_partial == 1 ? o_partial : 0;
            if (o) {
                s->opt = opt = o->val, s->longidx = o - longopts;
                if (argv[s->i][j] == '=') s->arg = &argv[s->i][j + 1];
                if (o->has_arg == 1 && argv[s->i][j] == '\0') {
                    if (s->i < argc - 1) s->arg = argv[++s->i];
                    else opt = ':'; /* missing option argument */
                }
            }
        }
    } else { /* a short option */
        const char *p;
        if (s->pos == 0) s->pos = 1;
        opt = s->opt = argv[s->i][s->pos++];
        p = strchr((char *) ostr, opt);
        if (p == 0) {
            opt = '?'; /* unknown option */
        } else if (p[1] == ':') {
            if (argv[s->i][s->pos] == 0) {
                if (s->i < argc - 1) s->arg = argv[++s->i];
                else opt = ':'; /* missing option argument */
            } else s->arg = &argv[s->i][s->pos];
            s->pos = -1;
        }
    }
    if (s->pos < 0 || argv[s->i][s->pos] == 0) {
        ++s->i, s->pos = 0;
        if (s->n_args > 0) /* permute */
            for (j = i0; j < s->i; ++j)
                ketopt_permute(argv, j, s->n_args);
    }
    s->ind = s->i - s->n_args;
    return opt;
}

#endif
